Fluorescent Probe Encapsulated in Avidin Protein to Eliminate Nonspecific Fluorescence and Increase Detection Sensitivity in Blood Serum

Quantitative detection of trace amounts- of a biomarker in protein rich human blood plasma using fluorescent probes is a great challenge as the real signal is usually obscured by nonspecific fluorescence. This problem occurs because most of the fluorescent dyes bind very tightly with blood proteins to produce a large fluorescence increase, resulting in overestimation of the biomarker concentrations and false positive diagnosis. In this paper, we report, that biotinylated fluorescent probes encapsulated in,avidity protein can generate very specific fluorescence in blood serum by blocking out nonspecific dye protein interactions. We applied our novel probe design to detect two different types of'biomolecules, hydrogen sulfide and nitroreductase. Out Avidin,conjugatecl probes achieved quantitative analyte detection in blood serum; whereas concentrations were overestimated up to 320-fold when bare fluorescent probes were employed. As compared to conventional approaches where fluorescent probes are encapsulated into polymers and nanoparticles, our simple approach successfully overcomes many key issues such as dye leakage, long preparation steps, inconsistent dye host ratios, difficiilty in constructing in situ in a complex medium, and limited application to detect only small metabolites.